The present invention relates to a device for working at a hard material, e.g. concrete or steel, by means of a jet stream containing an abrasive. By abrasive is meant a particle material, preferably sand.
In previously known devices of the above mentioned kind, see GB 2 162 778, one has used dry abrasive. An important disadvantage with dry abrasive is that the price is several times higher than for abrasive which can be allowed to be moist and also may contain minor contaminations. Furthermore, it is in certain applications difficult to keep the material dry.